A screening process to identify individuals who are at risk of developing Type I Insulin Dependent Diabetes Mellitus (IDDM). IDDM generally has its onset in young people and requires daily injections for insulin treatment. The development of IDDM is the result of the destruction of the insulin producing beta cells in the pancreas, a gland behind the stomach. The destructive process is thought to be caused by the immune system which ordinarily is involved in the body's defenses against disease and other environmental insults. In the case of IDDM, the immune system has reactions directed against one's own pancreas, specifically against the insulin producing beta cells within the pancreas. This destruction seems to take place over the course of several years. It is possible to detect evidence that this process has begun in some people. This study is designed to determine the degree of risk in such individuals, to study the nature of the immune mechanisms involved in the destructive process, and to determine if the process can be altered. The study will have three phases: screening, staging, and intervention. Subjects will be less than 45 years old and are first degree relatives of people with IDDM. Other relatives up to 20 years old will be screened. An initial collection of 10 ml of blood will be made to determine islet cell antibodies (ICA). Subjects with positive ICA will be eligible for phase two, staging. ICA is found in the blood of individuals who may develop diabetes years before they show symptoms. Staging identifies those ICA subjects who have an abnormal intravenous glucose tolerance test and a normal oral glucose tolerance test for randomization into intervention. The subjects will be seen at the General Clinical Research Center at MCV/VCU. On at least two different days, each following an overnight fast, The IV glucose tolerance test will be given. This helps determine the level of insulin response by the body. The second visit will be for the oral glucose tolerance test which will determine the level of glucose in the body in response to consumed glucose. Blood samples will be drawn. Also, from these studies, there is the hope of defining more precisely, the characteristics of those who will develop diabetes as well as the characteristics of those who do not.